The Rolls Royce/SNECMA Olympus 593 Mk 610

Rolls Royce Olympus history

The Olympus engine was first developed and produced by Bristol Aero Engines, based in Filton, England. The first use of the Olympus engine was as the powerplant for the Avro Vulcan "V" bomber . The first Olympus powered flight of the Vulcan prototype VX777 took place on 3rd September 1953, using four Olympus 100 engines, each generating 9750lb of thrust.

The initial production version of the Olympus was the Olympus 101, which generated 11,000lb of thrust. By the time Vulcan production ended in 1965, the Olympus 301 engine it was fitted with would generate 22,000lb of thrust, more then double that of the initial version.

Bristol Aero Engines merged with Armstrong Siddeley in 1959 to form Bristol Siddeley. The Olympus 593 project was started in 1964, using the Olympus 320 which had been developed for the cancelled BAC TSR.2 as the basis of the new engine. The development work was split 60-40 between Bristol Siddeley of Britain and SNECMA of France. When Rolls Royce aquired Bristol Siddeley in 1966, it continued as the British partner

Rolls Royce/SNECMA Olympus 593 development

The engineers had considered both Turbojet & Turbofan engines for use in SST (SuperSonic Transport) designs. It was decided that turbofans would not be advantageous in supersonic flight. Because of their large master cross-section they would cause excessive drag. Concorde ’s Russian equivelent, the Tupolev Tu 144 , did use Kuznetsov turbofans manufactured by Kuznetsov. But the Tupolev had to keep 40% reheat when cruising at Mach 2 to compensate for their drag. This limited the range drastically. Soon the engineers settled on the use of a turbojet.

At the time of their choice in 1962, the most powerful turbojet design in Europe was the Olympus, and this engine was chosen for further development for use on the Concorde project. To meet the needs of the Concorde , The Olympus required significant modifications, of which the main points were:

• A variable air inlet, to slow down the inlet airflow.
• A partial reheat, to provide more power during take-off, and during the transistion from subsonic to supersonic flight.
• The use of heat resistant materials to allow engine operation at the increased temperatures encountered during supersonic flight.
• Low fuel consumption, especially in Supersonic cruise

Also of note were the electronic control system used for the engine and it’s ancillaries, which was very advanced at the time.

Olympus 593 variable inlet assembley

The variable inlet assembley used on Concorde ’s Olympus engines is crucial to the performance of the engine in supersonic flight.

Turbojet engines cannot operate directly in supersonic airflow, so the variable inlet using variable convergent-divergent ramps was designed to slow the airflow, and regulate the flow of air reaching the compressor.

During take-off the inlet ramps are in the fully open position, to allow as much air as possible to reach the compressor. There is also an auxiliary inlet on the underside of the engine nacelle, which provides additional airflow. When the speed has increased to around Mach 0.7, (approx. 530 mph) this auxiliary inlet is closed.

When Mach 1.3 is reached, the inlet ramps start going down, limiting the compressor intake airspeed and therefore the mass flow. The ramps provide the engine with the correct amount of air required, while the remaining air is bypassed around the engine, and is used as cooling.

During cruise at around Mach 2, the inlet ramps are fully lowered, reducing the inlet air speed to around Mach 0.5 by the time it reaches the compressor. The ramps also bypass the turbulent boundary layer of the air intake around the turbine, allowing only smooth airflow to enter the compressor.

Olympus 593 reheat / afterburner

The reheat system fitted on the Olympus 593 Mk.610 provides a thrust boost of 22% for take-off and 30% for the transition from subsonic to supersonic flight. The reheat system comprises a single-ring fuel sprayer, flameholders and jet pipe liners. Its fuel flow is programmed as a fraction of the main fuel flow, and it also takes into account the engine inlet temperature.

The reheat system is used during take-off, and for transonic acceleration. Reheat is cut-off at speeds above Mach 1.7, and is not required during Mach 2 cruise. In the Olymous 593, the afterburner section is actually longer then the engine itself.

Olympus 593 testing

In June 1966 a complete Olympus 593 engine and variable geometry exhaust assembly was first run at Melun-Villaroche, France. On the British side, flight tests began at Filton, Bristol, using an RAF Vulcan bomber with the engine attached to its underside. Tests were limited to a speed of Mach 0.98 as the Avro Vulcan was not intended as a supersonic design. The Vulcan had been chosen as the testbed as it had sufficient ground clearance to allow the Olympus to be slung underneath. During these tests the Olympus 593 achieved 35,190 lb’s thrust.

Rolls Royce/SNECMA Olympus 593 Mk 610 Specifications

Robert Kent